title: Liver ABCA1 deletion in LDLrKO mice does not impair macrophage reverse cholesterol transport or exacerbate atherogenesis.
abstract: OBJECTIVE
  Hepatic ATP binding cassette transporter A1 (ABCA1) expression is critical for maintaining plasma high-density lipoprotein (HDL) concentrations, but its role in macrophage reverse cholesterol transport and atherosclerosis is not fully understood. We investigated atherosclerosis development and reverse cholesterol transport in hepatocyte-specific ABCA1 knockout (HSKO) mice in the low-density lipoprotein (LDL) receptor KO (LDLrKO) C57BL/6 background.
  
  
  RESULTS
  Male and female LDLrKO and HSKO/LDLrKO mice were switched from chow at 8 weeks of age to an atherogenic diet (10% palm oil, 0.2% cholesterol) for 16 weeks. Chow-fed HSKO/LDLrKO mice had HDL concentrations 10% to 20% of LDLrKO mice, but similar very low-density lipoprotein and LDL concentrations. Surprisingly, HSKO/LDLrKO mice fed the atherogenic diet had significantly lower (40% to 60%) very low-density lipoprotein, LDL, and HDL concentrations (50%) compared with LDLrKO mice. Aortic surface lesion area and cholesterol content were similar for both genotypes of mice, but aortic root intimal area was significantly lower (20% to 40%) in HSKO/LDLrKO mice. Although macrophage (3)H-cholesterol efflux to apoB lipoprotein-depleted plasma was 24% lower for atherogenic diet-fed HSKO/LDLrKO versus LDLrKO mice, variation in percentage efflux among individual mice was <2-fold compared with a 10-fold variation in plasma HDL concentrations, suggesting that HDL levels, per se, were not the primary determinant of plasma efflux capacity. In vivo reverse cholesterol transport, resident peritoneal macrophage sterol content, biliary lipid composition, and fecal cholesterol mass were similar between both genotypes of mice.
  
  
  CONCLUSIONS
  The markedly reduced plasma HDL pool in HSKO/LDLrKO mice is sufficient to maintain macrophage reverse cholesterol transport, which, along with reduced plasma very low-density lipoprotein and LDL concentrations, prevented the expected increase in atherosclerosis.
authors.affiliation: From the Section on Lipid Sciences, Department of Pathology (X.B., X.Z., M.D., E.Y.B., M.D.W., A.K.G., J.S.P.), and Department of Biochemistry (J.S.P.), Wake Forest School of Medicine, Winston-Salem, NC.
authors.forename: Xin
authors.initials: X
authors.lastname: Bi
authors.forename: Xuewei
authors.initials: X
authors.lastname: Zhu
authors.forename: MyNgan
authors.initials: M
authors.lastname: Duong
authors.forename: Elena Y
authors.initials: EY
authors.lastname: Boudyguina
authors.forename: Martha D
authors.initials: MD
authors.lastname: Wilson
authors.forename: Abraham K
authors.initials: AK
authors.lastname: Gebre
authors.forename: John S
authors.initials: JS
authors.lastname: Parks
mesh_terms: D064286:ATP Binding Cassette Transporter 1 / Q000172:deficiency* / Q000235:genetics; D000818:Animals; D001018:Aortic Diseases / Q000209:etiology / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D053299:Apolipoprotein B-100; D001055:Apolipoproteins B / Q000097:blood; D050197:Atherosclerosis / Q000209:etiology / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D001646:Bile / Q000378:metabolism; D001692:Biological Transport; D002460:Cell Line; D002784:Cholesterol / Q000097:blood / Q000378:metabolism*; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood; D015243:Cholesterol, VLDL / Q000097:blood; D004036:Diet, Atherogenic; D004195:Disease Models, Animal; D005243:Feces / Q000737:chemistry; D005260:Female; D008099:Liver / Q000378:metabolism*; D017737:Macrophages, Peritoneal / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011973:Receptors, LDL / Q000172:deficiency* / Q000235:genetics; D013997:Time Factors
chemical_list: D064286:ATP Binding Cassette Transporter 1; D053299:Apolipoprotein B-100; D001055:Apolipoproteins B; D002784:Cholesterol; D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D015243:Cholesterol, VLDL; D011973:Receptors, LDL; C577833:Abca1 protein, mouse; C415826:Apob protein, mouse
keywords: atherosclerosis; cardiovascular diseases; cholesterol; lipids; lipoproteins